In patients undergoing surgery, because of vasodilation induced by anesthetic agents and hypovolemia induced by surgical bleeding, hypotension is frequently observed during the surgical procedure. Prolonged hypotension may lead to organ hypoperfusion and at the end organ failure. Prompted therapeutic intervention to normalize blood pressure is therefore expected, and is based on volume loading and/or the administration of vasoactive or/and inotropic agents.
In some instances, anesthesiologists may be interested not only in maintaining blood pressure but also in maximizing stroke volume (or increasing stroke volume until stroke volume reaches a plateau). Indeed, in patients undergoing high-risk surgery, either because of chronic disease state (e.g. hip surgery in a patient with chronic heart failure) or acute disease state (e.g. peritonitis surgery in a patient with septic shock) or/and because of the surgical procedure itself (e.g. spine hemorrhagic surgery), it has been established that maximizing stroke volume by the mean of fluid administration may decrease the incidence of postoperative complications and reduce the length of stay in the intensive care unit and in the hospital (cost saving strategy).
In patients undergoing surgery, the identification of hypotensive patients who may benefit from volume loading and of those who may benefit from vasoactive or/and inotropic agents is very difficult. For example, vasoplegic states (which may benefit from vasoactive drug administration) can be identified by evaluating systemic vascular resistances but cardiac output—a parameter necessary for the calculation of systemic vascular resistances—is usually not measured during the surgical procedure.
Hypovolemic states can be identified by assessing blood volume, or cardiac dimensions, but it is usually not the case nor possible during the surgical procedure.
In patients undergoing high-risk surgery, maximizing stroke volume implies to measure stroke volume, which is not always the case or possible and requires the use of a specific and more expensive cardiac output monitoring technology.
Even when stroke volume and cardiac output can be measured and monitored during the surgical procedure, there is no system allowing the automatic control of fluid administration and vasoactive or/and inotropic agents administration, minimizing the duration of systemic hypotension, preventing the development of organ failure, and improving the outcome of patients undergoing surgery.